Arc lamp



Sept. 6, 1938. A. F. MARTIN 2,129,530

' ARC LAMP Filed Aug. 30, 1934 3 Sheets-Sheet l ALLAN F. MARTIN INVENTOR ATTORNEY Se t. 6, 1938.

Ill:

.27 Si 50 v 74 FlG.3 ALLAN F. MARTIN l9 INVENTOR ATTORNEY Sept. 6,, 1938.

' A. F. MARTIN ARC LAMP 3 Sheets-Sheet 3 Filed Aug. 30. 1934 FIG. 4

5 2. ss E ALLAN F. MARTIN INVENTOR BY @0141 ATTORNEY Patented Sept. 6, 193% Banscli & Lomb Optical Company, Rochester, N. Y., a corporation of New York Application August 3t), 1934, Serial No. 742,080

4 Claims.

The present invention relates to electric arc mechanisms and has for its object to provide improvements in mechanisms of this kind, par ticularly with respect to the feeding means for electrodes.

Another object of the present invention to provide a continuous and postlve driving oon= nection for the electrodes together with in proved means for advancing the same in the. di-

rection desired.

Another object of the present invention is to provide a feeding mechanism for the electrodes which will automatically move the electrodes in the desired direction and at the proper rate.

A further object of the invention is to provide mechanism for automatically disconnecting the driving connection to the electrodes when the electrodes are burned out or broken.

A further object of the present invention is to provide a safety device for opening the circuit in the event that the arc is extinguished.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the drawings:

Fig. 1 is a side elevation of a machine embodying one form of the invention.

Fig. 2 is a side view of the lamp with a side wall removed.

Fig. 3 is a top View of the lamp with the top wall removed.

Fig. 4 is a top view of the motor drive connections, partly in section. g

Fig. 5 is a section taken along line 55 of Fig. 2.

Fig. 6 is a diagrammatic view illustrating the chain drive for the electrodes.

Fig. 7 is one form of wiring diagram for the device, and

Fig. 8 is a simplified wiring diagram illustrating the theory of operation.

The present are mechanism is shown in connection with a projection apparatus for miscroscopic projection work whereby to illustrate one of a number of different kinds of machines with which the invention may be used. The projection I apparatus is illustrated generally at ID and includes a base II and an upstanding bracket l2 thereon carrying an objective lens holder I3 at one side thereof and a collar l4 at the opposite side which is adapted to receive an extension l5 on lamp box IE-when the lamp box is in operative relation to the projection apparatus. The lamp box IE is formed with a base I! and an upstanding portion l8 containing the extension 15, adjustable observation windows l9 for observing the electrodes, a ventilating opening I 8A and bafiles [9A to permit the escape of heat.

A housing 20 contains the electrodes 2| and 22 and the mechanism for feeding the electrodes and is provided with a slot 23 cooperating with a'pin Ed on the base i'l so that the housing may be siidably moved with respect to said base. The base 2'? is cut away at it so that the housing may pivot about'the pin M. The housing is provided with a bottom wall. 1'35, side walls and a back wall and a top wall hinged at it and provided with a knob iii to permit access into the interior of the casing. A handle is fixed to the rear wall 28 for moving the housing with respect to the lamp box.

The horizontally disposed electrode M is removably mounted in a suitable holder 33 and the vertical electrode 22 in a similar holder 34, these holders being slidably disposed preferably upon a pair of horizontal guide rods 35 and a pair of vertical guide rods 35, respectively. The outer ends of the guide rods 35 are suitably connected with a member 31 held fixed within the casing by means of a pin 3li extending between walls 25 and 21, and the vertical guide rods 35 are similarly connected with a member 39 held within the housing by a pin 45 as shown in Fig. 2. Both sets of guide rods have their inner or adjacent ends anchored in a block M of heat resistant material which is fastened within the housing by means of a pin 42 and which is provided with an apertured extension 43 to serve as a support and guide for the upper electrode 21.

The means for advancing the electrode supports 33 and 34 preferably comprise a flexible operating member 44 in the form of a continuous chain or'like connection, with means for positively driving the same which will hereinafter be described. The chain or flexible connection is extended over a series of pulleys or rollers comprising upper and lower rollers 45 and 46, a pair of intermediate rollers 41 and 48 adjacently mounted upon a support 49 which is suitably secured to walls 26 and 21, a third intermediate roller 50 mounted upon a support 5|, and a drive sprocket 52. The rollers 45 and 46 are suitably mounted upon transversely extending shafts 53 and 5.4 which are suitably secured to the side walls 26 and 21. The chain is directly connected to the electrode supports 33 and 34 by means of studs 55 so that it willadvance each at the same rate of speed and thereby maintain the free ends of the electrodes at the desired distance apart.

As best shown in Fig. 4, an electric motor 56, through reduction gearing 51 drives a shaft 58 upon which the drive sprocket 52 is loosely mounted adjacent a collar 59 fixed to the shaft. Extending from the end of shaft 58 and fixed thereto is a threaded member 60 upon which is threaded a thumb nut lit for forcing the sprocket 52 into driving engagement with the fixed collar 55. The member 60 is provided with an enlarged head 62 to prevent removal of the thumb nut 6!. The threads upon member 60 are so arranged that when the electrodes are feeding,

the motor drive tends to loosen the thumb nut and declutch the drive'sprocket. Thus, when the electrodes are burned out and electrode support 33 or 34 abuts block 4|, the drive sprocket will be declutched before any damage can be done to the chain or other mechanism. The motor 58 extends through an opening 53 in the side wall 26 and is protected by a removable cover plate 64.

The electrode supports 33 and 34 are substantially identical and only one will be described. The support 33 is provided with a pair of longitudinal bores 55 to slidably receive the guide rods 35 and a third longitudinal bore 66 for receiving the electrode 2|. A transverse slot 51 extends from the top of the support down past the upper side of the'electrode. A leaf spring BBis fixed to the support at 65 and has its free end bearing against the electrode to form a resilient attaching means for the electrode. Two insulating washers I0 and H fastened together to the bottom of the support 33 by means of a screw 12 form stud 55 for rigidly connecting the support 33 to the chain 44.

A pair of thumb wheels 13 and H are connected to shaft 53 and pulley 35 for manually moving the driving chain 44 and electrode supports 33 and 34 when the sprocket 52 is declutched from shaft 58.

Referring now to the electrical system shown in Fig. 7, current is supplied to the system through supply wires 15 and 16 through relay switch 11 and holding coil 18. The two variable resistances l9 and are connected in series across the line and the arc 8|, variable resistance 82 and fixed resistance 33 are likewise connected in series across the line and are in parallel with variable resistances I9 and 80. The motor field coil II is connected in parallel with resistance 80 and the motor armature is connected be- I tween resistances 19 and 80 on one side and between the arc 8| and resistances 82 and 83 on the other side. A relay coil 86 energized by switch II for actuating relay switch 11 is connected across the supply wires I5 and 16 in parallel with the remainder of the system. The holding coil 18 is sufficient to hold switch 1! closed only when the arc is burning.

The theory and operation can best be understood from the schematic wiring diagram of Fig. 8. The various elements and resistances are connected across the supply wires 15, IS in the form of a Wheatstone bridge. The four arms of the bridge are resistance 19, held 84 and resistance Ill, resistances 82 and 83 and the arc 8|, the

motor armature 85 being connected across the bridge as shown. Resistances I9 and 80 are ad- Justed once to balance the system but are not moved during the operation of the lamp. Resistmice 82 controls the intensity of the arc. Thus it is obvious that the amount of current flowing through the arc will regulate the direction and amount of the current flowing through the armature.

In operation the operator depresses switch 81 which, through relay coil 88 closes switch H to initiate operation of the motor 56. The motor. through sprocket 62 and chain 44, will feed the electrodes 2| and 22 toward each other until the arc is struck. The switch 81 is then released and the are which has been drawing no current draws a large amount when the electrodes come in contact with each other. This rush of current changes the current distribution of the Wheatstone bridge and causes the motor to re verse and draw the arc to its proper length. When this state is reached, the bridge is in complete balance and no current flows through the motor armature. As soon as the arc gets too long due to the burning away of the electrodes the bridge is again unbalanced and current will flow through the motor armature to move the electrodes until a state of balance is again reached.

The are may be shut off at any time by a suitable switch, not shown, in the main power circuit.

Although I have shown my invention as applied to an arc lamp for a microprojector it is obvious that it could be applied to any electric are such as a street lamp, spectroscope are or the like. Various modifications can, of course, be made without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. An arc lamp comprisinga main housing having a base, a front wall provided with a light opening, two side walls, one being provided with a sight opening, a top wall provided with an opening to permit the escape of heat, an auxiliary housing pivotally and slidably mounted upon said main housing to close the rear thereof, an electric are mounted in said auxiliary housing, and means for moving said auxiliary housing into said main housing so that the arc may be observed through said sight opening.

2. A lamp housing comprising a main housing having a base, an apertured front wall, a top wall, two side walls and an open rear wall, and an auxiliary housingpivotally and slidably mounted upon said base for closing said open rear wall, a movable top on said auxiliary housing and means on said auxiliary housing for pivotally and longi' tudinally moving it with respect to said base.

3. An arc lamp comprising a, base, a main housing at the front end of said base, said housing having a front wall provided with a light opening, two side walls, a top wall provided with an opening to permit the escape of heat, an auxiliary housing having two side walls and a rear wall, a pair of electrodes movably mounted in said auxiliary housing for movement toward and from each other, means carried by said auxiliary housing for feeding the electrodes toward each other, a cover carried by said auxiliary housing, and means for slidably securing said auxiliary housing on said base, for movement of the auxiliary housing into and out of the main housing.

4. An arc lamp comprising a base, a main housing at the front end of said base, said housing having a front wall provided with a light opening, two side walls, a top wall provided with an opening to permit the escape of heat, an auxiliary housing having two side walls and a rear wall, a pair of electrodes movably mounted in said auxiliary housing for movement toward and from each other, means carried by said auxiliary housing for feeding the electrodes toward each other, a cover carried by said auxiliary housing. longitudinal slots in the side walls of the auxiliary housing, and a pin extending loosely through said slots and secured in the side walls of the main housing for slidably and pivotally securing said auxiliary housing to said main housing.

ALLAN F. MARTIN. 

